Vacuum cleaners typically use a suction nozzle that is movable across a surface to be cleaned. The suction created at an inlet in the nozzle results in the removal of free dirt particles accumulated on the surface. However, ground in dirt is frequently encountered when cleaning carpets or other textured surfaces, and reliance on suction for removal of such ground-in dirt has proven to be unsatisfactory.
Vacuum cleaners are provided with devices that agitate the carpet surface to dislodge ingrained dirt particles. For example mechanical beaters, which physically strike the carpet surface to loosen dirt particles. Such agitators are often located on the vacuum cleaner nozzle head, so that dirt can be dislodged and instantly removed by moving the nozzle head across a soiled carpet surface. An example of a mechanical beater is a cylindrical rotatable beater brush having a plurality of extending resilient bristles and prongs that physically beat the carpet as the nozzle head is moved.
A recent trend in carpet manufacturing is soft carpets, which are made of softer yarns. Denier quantifies the softness of the yarn, and is the weight in grams of 9,000 meters of the yarn. The larger the denier, the thicker the yarn. Denier per filament (DPF) represents the size of an individual filament of the yarn. The lower the DPF, the softer the fiber. Traditional home carpets have a DPF of between approximately 12-18. The new soft carpet trend has resulted in carpets having a DPF between approximately 3.5 to 4.5. These soft yarns can have three to four times as many filaments as in the traditional home carpets. Traditional strands of yarn have approximately 120 filaments. The soft strands of yarn can have approximately 700 or more filaments.